Support Bracket for Selective Fire Switches

ABSTRACT

Disclosed is a robust selective fire switch. One exemplary selective fire switch includes a switch housing, a plunger having a head and a body extending longitudinally from the head, the head extending at least partially into an opening defined in the switch housing, a first post and a second post arranged on opposing sides of the switch housing, and a filament wire coupled to and extending between both the first and second posts, the filament wire being in contact with the plunger and thereby securing the plunger in a seated configuration within the switch housing.

BACKGROUND

The present disclosure relates generally to wellbore casing perforationoperations and, more particularly, to a more robust selective fireswitch used in casing perforating guns.

After drilling the various sections of a subterranean wellbore thattraverses a hydrocarbon-bearing formation, individual lengths ofrelatively large diameter metal tubulars are typically secured togetherto form a casing string that is positioned within the wellbore. Thiscasing string increases the integrity of the wellbore and provides apath for producing fluids extracted from producing intervals in theformation to the surface. Conventionally, the casing string is cementedwithin the wellbore. To produce fluids into the casing string, hydraulicopenings or perforations must be made through the casing string and thecement, and extend a short distance into the surrounding subterraneanformation.

Typically, these perforations are created by detonating a series ofshaped charges that are disposed within the casing string and arepositioned adjacent to the formation. Specifically, one or moreperforating guns are loaded with shaped charges that are connected witha detonator via a detonating cord. The perforating guns are thenconnected within a tool string that is lowered into the cased wellboreat the end of a tubing string, wireline, slickline, coiled tubing orother type of downhole conveyance. Once the perforating guns areproperly positioned in the wellbore such that the shaped charges areadjacent the formation to be perforated, the shaped charges aredetonated, thereby creating the desired hydraulic openings in to thecasing string.

To detonate a particular shaped charge, a voltage is commonly sent to acorresponding selective fire switch that includes a filament wireconfigured to be burned or otherwise disintegrate upon being subjectedto a predetermined amount of voltage. The filament wire also typicallysupports a plunger used to switch the fire switch into detonation mode.Once the filament wire is burned, the plunger is able to switchpositions, thereby placing the fire switch in detonation mode. Intraditional selective fire switches, the filament wire is usuallysupported with a pliable terminal or turret and may be susceptible totensile stresses and environmental vibrations. Upon experiencing extremevibrations, for example, especially vibrations stemming from adjacentdetonations or explosions, the filament wire can fail or may otherwisebe rendered inoperable before its intended operation can be carried out.

SUMMARY OF THE DISCLOSURE

The present disclosure relates generally to wellbore casing perforationoperations and, more particularly, to a more robust selective fireswitch used in casing perforating guns.

In some embodiments, a selective fire switch is disclosed and mayinclude a switch housing, a plunger having a head and a body, the bodyextending longitudinally from the head and at least partially into anopening defined in the switch housing, a first post and a second postarranged on opposing sides of the switch housing, and a filament wirecoupled to and extending between both the first and second posts acrossthe switch housing, the filament wire being in contact with the plungerand thereby securing the plunger in a seated configuration within theswitch housing.

In some embodiments, a method of operating a selective fire switch isdisclosed. The method may include securing a plunger in a seatedconfiguration within a switch housing with a filament wire that engagesthe plunger, the filament wire being coupled to and extending between afirst post and a second post arranged on opposing sides of the switchhousing and extending across the switch housing, applying a voltageacross the filament wire, burning the filament wire with the voltage,and moving the plunger from the seated configuration to an extendedconfiguration with respect to the switch housing.

In some embodiments, another selective fire switch is disclosed and mayinclude a switch housing, a plunger extending at least partially into anopening defined in the switch housing, an input stanchion and an outputstanchion arranged on a first side of the switch housing, the input andoutput stanchions being electrically conductive and structurally offsetfrom each other, a post arranged on a second side of the switch housingopposite the first side of the switch housing, and a filament wirehaving a first portion coupled to the input stanchion and extending tothe post across the switch housing, and a second portion extending fromthe post across the switch housing and to the output stanchion, thefilament wire being in contact with the plunger and thereby maintainingthe plunger in a seated configuration within the switch housing.

The features of the present disclosure will be readily apparent to thoseskilled in the art upon a reading of the description of the embodimentsthat follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of thepresent disclosure, and should not be viewed as exclusive embodiments.The subject matter disclosed is capable of considerable modifications,alterations, combinations, and equivalents in form and function, as willoccur to those skilled in the art and having the benefit of thisdisclosure.

FIG. 1 is a well system that may embody or otherwise employ one or moreprinciples of the present disclosure, according to one or moreembodiments.

FIGS. 2A-2D are various views of an exemplary selective fire switch,according to one or more embodiments.

FIGS. 3A and 3B are isometric views of another exemplary selective fireswitch, according to one or more embodiments.

FIGS. 4A-4D illustrate various exemplary embodiments of a plunger thatcan be used with the selective fire switches of FIGS. 2A-2D or 3A-3B,according to one or more embodiments.

DETAILED DESCRIPTION

The present disclosure relates generally to wellbore casing perforationoperations and, more particularly, to a more robust selective fireswitch used in casing perforating guns.

The present disclosure describes a selective fire switch that hasstructural stanchions or posts configured to reliably support a filamentwire that is to be burned or otherwise disintegrated in the process ofsetting a detonator. The posts provide additional structural strength tothe switch and the filament wire such that the filament wire is able tosustain heavy shock loads and vibrations, such as vibrations that aresustained through detonations of adjacent perforation charges. Moreover,the posts may include lateral extensions that bend over or extend acrossthe switch a short distance in order to decrease the deflectionpotential of the filament wire, thereby reducing the potential fortensile fatigue in the filament wire before its intended operation canbe undertaken.

Referring to FIG. 1, illustrated is a well system 100 that may embody orotherwise employ one or more principles of the present disclosure. Thewell system 100 may include an offshore oil and gas platform 102centered over a submerged oil and gas formation 104 located below a seafloor 106. Even though FIG. 1 depicts an offshore oil and gas platform102, it will be appreciated by those skilled in the art that the variousembodiments discussed herein are equally well suited for use inconjunction with other types of oil and gas rigs, such as land-based oiland gas rigs or rigs located at any other geographical site. A subseaconduit 108 extends from a deck 110 of the platform 102 to a wellheadinstallation 112 including one or more subsea blow-out preventers 114.The platform 102 has a hoisting apparatus 116 and a derrick 118 forraising and lowering pipe strings, such as work string 120, within thesubsea conduit 108.

As depicted, a wellbore 122 extends through the various earth strataincluding a hydrocarbon-bearing formation 104. A casing string 124 iscemented within the wellbore 122 using cement 126. The work string 120includes various tools such as a plurality of perforating gun assemblies134 arranged at or near its distal end. When it is desired to perforatethe casing string 124 and cement 126 in order to provide fluidcommunication to the formation 104, the work string 120 is loweredthrough the casing string 124 until the perforating guns 134 areproperly positioned relative to the formation 104. Thereafter, one ormore shaped charges within the string of perforating guns aresequentially fired, either in an uphole to downhole or a downhole touphole direction. Upon detonation, the liners of the shaped charges formjets that create a spaced series of perforations extending outwardlythrough the casing string 124, the cement 126, and into surroundingportions of the formation 104, thereby allowing fluid communicationbetween the formation 104 and the wellbore 122.

In the illustrated embodiment, the wellbore 122 has an initial,generally vertical portion 128 and a lower, generally deviated orhorizontal portion 130. The work string 120 may include a retrievablepacker 132 which may be sealingly engaged with the casing string 124 inthe vertical portion 128 of the wellbore 122. The perforating guns 134may have a ported nipple 136 arranged at their upper or proximal end,below which is a time domain firer 138. The time domain firer 138 may bearranged at the upper end of a tandem gun set 140 including first andsecond guns 142 and 144. In the illustrated embodiment, a plurality ofsuch gun sets 140 are utilized, each including a first gun 142 and asecond gun 144.

Positioned between each gun set 140 may be a blank pipe section 146 usedto control and optimize the pressure conditions in the wellbore 122immediately after detonation of the shaped charges. In otherembodiments, the blank pipe sections 146 may serve as secondary pressuregenerators. It should be understood by those skilled in the art that anyarrangement of perforating guns may be utilized in conjunction with thepresent disclosure, including both more and less sections of blank pipe146 as well as no sections of blank pipe 146, without departing from thescope of the disclosure. It will also be appreciated by those skilled inthe art that even though FIG. 1 depicts the perforating guns 134 and itsassociated components as being arranged to perforate a horizontalsection of the wellbore 122, the embodiments described herein areequally applicable for use in portions of the wellbore 122 that arevertical, deviated, slanted or otherwise.

Referring now to FIGS. 2A-2D, illustrated are various views of anexemplary selective fire switch 200 (hereinafter “switch”) that may beused in conjunction with one or more of the perforating guns 134 of FIG.1, according to one or more embodiments. In particular, FIGS. 2A and 2Billustrate isometric and end views of the switch 200, respectively, in asecured configuration (i.e., a position opposing a load), and FIGS. 2Cand 2D illustrate isometric and end views of the switch 200,respectively, in an actuated configuration (i.e., a position afterfunctioning). Those skilled in the art, will readily recognize that theembodiments disclosed herein may equally be applied to other technologyfields besides the oil and gas industry. Indeed, the various embodimentsof selective fire switches disclosed herein may be used in any fieldwhere it may prove advantageous to have a robust and reliable firingswitch. For example, the exemplary selective fire switches may be usedin any device requiring a mechanism capable of enabling/disabling orengaging/releasing something.

The switch 200 depicted in FIGS. 2A-2D may include a switch housing 202coupled to or otherwise supported by a circuit board 204, such as aprinted circuit board or the like. The switch housing 202 may be made ofone or more non-conductive or insulative materials such as, but notlimited to, plastics, polymers, ceramics, glasses, composites,combinations thereof, and the like. The switch 200 may include a plunger206 at least partially arranged within the housing 202 and movablebetween a seated configuration, as depicted in FIGS. 2A and 2B, and anextended configuration, as depicted in FIGS. 2C and 2D. The plunger 206may also be made of one or more non-conductive or insulative materialssuch as, but not limited to, plastics, polymers, ceramics, glasses,composites, nylon, combinations thereof, and the like.

The plunger 206 may have a head 208 and a body 210 (FIG. 2B) thatextends longitudinally from the head 208. As depicted in FIG. 2B, thebody 210 may be configured to extend within an opening 212 defined orotherwise formed within the housing 202. The head 208 may exhibit adiameter that is greater than the diameter of the opening 212 such thatthe head 208 is prevented from extending into the opening 212 andotherwise generally rests on the exterior of the housing 202 when theplunger 206 is in its seated configuration.

The switch 200 may further include a filament wire 214 that may extendacross at least a portion of the housing 202 and may be supported acrossthe housing 202 by at least a first post 216 a and a second post 216 b.The filament wire 214, also known as a fuse wire or heater wire, mayalso be configured to at least partially maintain or otherwise securethe plunger 206 in its seated configuration within the housing 202. Insome embodiments, for example, the plunger 206 may define or otherwiseinclude at least one groove 218 configured to receive or engage thefilament wire 214. In the embodiment of FIGS. 2A-2D, for instance, theat least one groove 218 may include a first groove 218 a and a secondgroove 218 b defined on opposing sides of the head 208 and portions ofthe filament wire 214 may rest on or otherwise be received in each ofthe first and second grooves 218 a,b.

The filament wire 214 is shown in FIGS. 2A-2D as extending from thefirst post 216 a to the second post 216 b, extending around the secondpost 216 a and returning to the first post 216 a. Those skilled in theart will readily appreciate, however, that the filament wire 214 mayextend between the first and second posts 216 a,b in various otherconfigurations, without departing from the scope of the disclosure. Insome embodiments, for example, the filament wire 214 may include only asingle wire strand extension that extends between or otherwise connectsthe first post 216 a to the second post 216. As a result, and as will bedescribed in greater detail below, the at least one groove 218 may takeon several different configurations to accommodate the differingconfigurations of the filament wire 214, without departing from thescope of the disclosure.

In its seated configuration, as shown in FIG. 2B, the distal end of thebody 210 of the plunger 206 may engage or otherwise bias a togglemechanism 220. In some embodiments, the toggle mechanism 220 may be asingle-throw, single-pole switch, as generally known by those skilled inthe art. In other embodiments, the toggle mechanism 220 may encompassany other type of toggling or switching device capable of generallyperforming the actions of the toggle mechanism 220 described herein,such as relays, contactors, actuators, spring devices, valves,inflatable or expandable apparatus (whether inflating speed control ornot), and the like. In at least one embodiment, the toggle mechanism 220may be similar to or otherwise related to the switches described inco-owned U.S. patent application Ser. No. 13/494,075, filed on Jun. 12,2012, the contents of which are hereby incorporated by reference intheir entirety. Accordingly, the toggle mechanism 220 depicted in FIGS.2B and 2D is shown and described merely for illustrative purposes andshould not be considered limiting to the scope of the disclosure.

As illustrated, the exemplary toggle mechanism 220 may include a wiper222 that may be movable between a first position, as shown in FIG. 2B,where the wiper 222 makes contact with a first contact 224 a, and asecond position, as shown in FIG. 2D, where the wiper 222 makes contactwith a second contact 224 b. The wiper 222 may be spring biased orotherwise naturally tending towards contact with the second contact 224b. The wiper 222 may be made of an electrically conductive material,such as copper or bronze. In at least one embodiment, the wiper 222 maybe a wire or the like.

In order to maintain the wiper 222 in the first position or otherwise incontact with the first contact 224 a, the body 210 of the plunger 206may be extended through the opening 212 such that it engages the wiper222 and overcomes its spring force until the wiper 222 makes contactwith the first contact 224 a. In such a configuration, the plunger 206is in its seated configuration and may be maintained therein with thefilament wire 214 biasing against a portion of the head 208, such as theat least one groove 218. In the event the filament wire 214 is severedor otherwise fails, such as is depicted in FIGS. 2C-2D, the plunger 206may be moved or otherwise forced in the upward direction as the wiper222 moves to its second position and makes contact with the secondcontact 224 b.

The filament wire 214 may be coupled to or otherwise attached to thefirst and second posts 216 a,b which generally serve as stanchions thatsupport the filament wire 214 across the housing 202 and hold thefilament wire 214 in a substantially tangential relationship with thehead 208 of the plunger 206. As illustrated, the first and second posts216 a,b may be arranged on opposing sides of the housing 202 such thatthe filament wire 214 generally extends across the top of the housing202. In some embodiments, the filament wire 214 may be soldered, welded,or brazed to one or both of the first and second posts 216 a,b, orotherwise attached thereto using a glue or any chemical adhesive knownto those skilled in the art. In other embodiments, the filament wire 214may be fastened to one or both of the first and second posts 216 a,busing one or more mechanical fasteners such as, but not limited to,screws, clamps, wedges, rivets, clips, heat shrink tubing, combinationsthereof, and the like. In yet other embodiments, the filament wire 214may form an integral part of one or both of the first and second posts216 a,b, without departing from the scope of the disclosure.

At their respective bases, the first and second posts 216 a,b may besoldered to, mechanically fastened to, or otherwise form an integralpart of the circuit board 204. In some embodiments, both the first andsecond posts 216 a,b may be electrically conductive or otherwise made ofa material that is able to conduct an electrical current therethrough.In other embodiments, however, one of the first or second posts 216 a,bmay be non-conductive or otherwise made of an insulative material,without departing from the scope of the disclosure. In the illustratedembodiment, both the first and second posts 216 a,b are electricallyconductive, as will be described below.

In one or more embodiments, at least one of the first and second posts216 a,b may include or otherwise define a lateral extension that extendsor otherwise reaches a short distance across or over the housing 202. InFIGS. 2A-2D, each of the first and second posts 216 a,b are depicted ashaving a lateral extension, labeled as a first lateral extension 226 aand a second lateral extension 226 b. The first and second lateralextensions 226 a,b may prove advantageous in providing additionalsupport to the filament wire 214 such that the filament wire 214 may beless susceptible to wire fatigue or mechanical vibrations. The distancethat each lateral extension 226 a,b extends across or over the housing202 may vary, depending on the application. In at least one embodiment,for example, one or both of the lateral extensions 226 a,b may extend tobut not obstruct movement of the plunger 206 such that the plunger 206is nonetheless able to move to its extended configuration.

According to one or more embodiments of the disclosure, the switch 200may be used to set or otherwise arm an igniter or detonator (not shown)used to detonate a corresponding perforating charge (not shown), such asis used in casing perforating operations briefly described above. Withthe switch 200 and the plunger 206 in their secured and seatedconfigurations, respectively, as depicted in FIGS. 2A and 2B, exemplaryoperation of the switch 200 is now provided.

A first voltage 227 may be sent to the toggle mechanism 220 via a powerline 228. The power line 228 may be communicably or otherwiseelectrically coupled to a power source (not shown) either arrangedadjacent the switch 200 (e.g., downhole) or at a remote location (e.g.,via wireline, slickline, e-line, etc.), such as the platform 102 ofFIG. 1. The first voltage 227 may be a positive or a negative voltage,depending on the perforating application and how many switches 200 areto be activated. Those skilled in the art will readily appreciate thatthe power line 228 may receive the first voltage 227 via severaldifferent methods or devices, without departing from the scope of thedisclosure.

With the plunger 206 in its seated configuration, the wiper 222 is heldin its first position and therefore in contact with the first contact224 a. Accordingly, the first voltage 227 is conveyed to the firstcontact 224 a which may be configured to convey the first voltage 227 toa first conductor line 230 a. In some embodiments, the first conductorline 230 a may be communicably or otherwise electrically coupled to thefirst post 216 a, such that the first voltage 227 is conveyed to thefirst post 216 a via the first conductor line 230 a. As shown in FIG.2A, the first conductor line 230 a is shown as extending to the firstpost 216 a as part of the design of the circuit board 204. At least onediode 232 (FIG. 2A) may be arranged in the first conductor line 230 aand otherwise configured to determine the polarity of the first voltage227 such that the correct voltage polarity is provided to the first post216 a for proper operation.

With continued reference to FIG. 2A, in some embodiments the firstvoltage 227 may be applied across the first post 216 a and to thefilament wire 214 which conveys the first voltage 227 to the second post216 b. In some embodiments, the filament wire 214 may extend at leastpartially down the first post 216 toward the circuit board 204. Thesecond post 216 b may then convey the first voltage 227 downstream toground, for example. The filament wire 214 may be manufactured orotherwise configured to exhibit a predetermined resistance per unitlength. The first voltage 227 may be a predetermined voltage used toovercome the predetermined resistance of the filament wire 214 such thatas the first voltage 227 is applied across the filament wire 214, thefilament wire 214 may be configured to burn, disintegrate, or otherwisefail.

Those skilled in the art will readily recognize the several advantagesof the first and second posts 216 a,b. For example, the first and secondposts 216 a,b may reliably secure the filament wire 214 across the topof the housing 202 while holding the plunger 206 in its seatedconfiguration. Moreover, the first and second posts 216 a,b provideadditional structural strength to the switch 200 and the filament wire214 such that the filament wire 214 may be able to sustain heavy shockloads and vibrations. The lateral extensions 226 a,b of each post 216a,b, respectively, may serve to decrease the length and deflection ofthe filament wire 214, thereby reducing the potential for tensilefatigue, commonly referred to as “support post fatigue.” As a result,the switch 200 provides a more robust and reliable means of setting adetonator.

Referring to FIGS. 2C-2D, the filament wire 214 is depicted as burned orotherwise disintegrated after having been subjected to the first voltage227. Without the filament wire 214 securing or maintaining the plunger206 in its seated configuration, the spring force of the wiper 222 mayovercome the weight of the plunger 206, thereby moving the plunger 206to its extended configuration as the wiper 222 moves to its secondposition. With the wiper 222 in its second position, contact is madebetween the wiper 222 and the second contact 224 b and the power source(not shown) is thereby placed in electrical communication with theigniter or detonator (not shown). Specifically, the power line 228 maybe electrically coupled through the wiper 222 and the second contact 224b to a second conductor line 230 b which may be coupled to thedetonator.

To activate the detonator, and thereby detonate a correspondingperforating charge, a second voltage 234 may be applied across the powerline 228 and conveyed through the wiper 222, the second contact 224 b,and the second conductor line 230 b which applies the second voltage 234to the detonator. Similar to the first voltage 227, the second voltage234 may be a positive or a negative voltage, depending on theperforating application and how many switches 200 are to be activated.

Referring now to FIGS. 3A and 3B, illustrated are isometric views ofanother exemplary selective fire switch 300 (hereinafter “switch”),according to one or more embodiments. The switch 300 may be similar insome respects to the switch 200 of FIGS. 2A-2D and therefore may be bestunderstood with reference thereto, where like numerals indicate likeelements that will not be described again in detail. Similar to theswitch 200 of FIGS. 2A-2D, the switch 300 includes the switch housing202 coupled to or otherwise supported by the circuit board 204. Theswitch 300 may also include the plunger 206 at least partially arrangedwithin the housing 202 and movable between seated and extendedconfigurations, as depicted in FIG. 3A and FIG. 3B, respectively.

Unlike the switch 200 of FIGS. 2A-2D, however, the first post 216 a ofthe switch 300 may include or otherwise encompass an input stanchion 302a and an output stanchion 302 b. As illustrated, the input stanchion 302a may be communicably or otherwise electrically coupled to the firstconductor line 230 a. The output stanchion 302 b may be structurallyoffset from the input stanchion 302 a and otherwise insulated fromcontact with the input stanchion 302 a except for through the filamentwire 214, as will be described below. Both the input and outputstanchions 302 a,b may be electrically conductive or otherwise made of amaterial that is able to conduct an electrical current. The second post216 b may or may not be electrically conductive. In embodiments wherethe second post 216 b is electrically conductive, any voltages appliedacross the second post 216 b may be prevented from passing through andinto the circuit board 204.

In some embodiments, the filament wire 214 may be soldered, welded, orbrazed to one or both of the input and output stanchions 302 a,b. Inother embodiments, the filament wire 214 may be fastened to one or bothof the input and output stanchions 302 a,b using one or more mechanicalfasteners such as, but not limited to, screws, clamps, wedges, rivets,clips, combinations thereof, and the like. In yet other embodiments, thefilament wire 214 may form an integral part of one or both of the inputand output stanchions 302 a,b. Moreover, one or both of the input andoutput stanchions 302 a,b may include or otherwise define a portion ofthe first lateral extension 226 a. In the illustrated embodiment, eachof the input and output stanchions 302 a,b are shown as definingcorresponding portions of the first lateral extension 226 a.

In the illustrated embodiment, the first voltage 227 may be conveyed tothe input stanchion 302 a via the first conductor line 230 a. The inputstanchion 302 a may apply the first voltage 227 across the filament wire214 and, more particularly, to a first portion 304 a of the filamentwire 214 that extends from the input stanchion 302 a, across the housing202, and to the second post 216 b. The filament wire 214 may then looparound the second post 216 such that the first voltage 227 is conveyedback to the first post 216 a or, more particularly, to the outputstanchion 302 b via a second portion 304 b of the filament wire 214.More particularly, the second portion 304 b may be configured to extendfrom the second post 216 b, across the housing 202, and to the outputstanchion 302 b. The output stanchion 302 b may convey the first voltage227 downstream, such as to ground, for example.

As briefly discussed above, the filament wire 214 may be manufactured orotherwise configured to exhibit a predetermined resistance per unitlength, and the first voltage 227 may be a predetermined voltage used toovercome the predetermined resistance of the filament wire 214. As aresult, as the first voltage 227 is conducted through the filament wire214, the filament wire 214 may be configured to burn, disintegrate, orotherwise fail, thereby freeing the plunger 206 to move into itsextended configuration, as depicted in FIG. 3B.

Those skilled in the art will readily appreciate that looping thefilament wire 214 around the second post 216 via the first and secondportions 304 a,b of the filament wire 214 requires the first voltage 227to traverse a greater effective length of the filament wire 214.Increasing the effective length of the filament wire 214 may increaseits resistance such that a reduced amount of voltage would be requiredto burn or otherwise disintegrate the filament wire 214.

Moreover, looping the filament wire 214 around the second post 216 viathe first and second portions 304 a,b also offers an increased amount ofstrength for the filament wire 214 such that the filament wire 214 maybe better able to sustain vibrations and other shock loading that may beencountered in a downhole environment.

Referring now to FIGS. 4A-4D, with continued reference to the priorfigures, illustrated are exemplary embodiments of the plunger 206,according to one or more embodiments. Each of the variations of theplunger 206 in FIGS. 4A-4D may be used in conjunction with any of theembodiments of the switches 200, 300 described above. As illustrated, insome embodiments of the plunger 206, the filament wire 214 may includetwo lengths of wire, each of which may be configured to apply voltage ineither the same or opposing directions across the plunger 206.Accordingly, in at least one embodiment, the filament wire 214 depictedin FIGS. 4A-4D may be the first and second portions 304 a,b of thefilament wire 214, as described above with reference to FIGS. 3A and 3B.In other embodiments, such as is shown in FIG. 4D, the filament wire 214may encompass a single wire strand that extends across the plunger 206.

In FIG. 4A, the at least one groove 218 may be centrally defined orotherwise formed on the head 208 of the plunger 206. The filament wire214 may rest within or otherwise be restrained within the groove 218until burned or disintegrated, as described above. As depicted, thegroove 218 may be in the general shape of a rectangular cut or slotdefined in the head 208. In other embodiments, however, the groove 218may be arcuate in shape (i.e., “U” shaped), such that the filament wire214 rests in a trough-like structure. In yet other embodiments, thegroove 218 may be “V” shaped or assume any other polygonal shape capableof receiving or otherwise containing the filament wire 214.

In FIG. 4B, the groove 218 may be entirely omitted from the plunger 206,and the filament wire 214 may instead rest or otherwise extend acrossthe top of the head 208. In FIG. 4C, the at least one groove 218 may becharacterized as one or more perforations or conduits defined in andotherwise extending through the head 208 of the plunger 206. Asillustrated in FIG. 4C first and second conduits 402 a and 402 b mayeach be configured to receive a separate strand of the filament wire 214therethrough. As will be appreciated, more or less than two conduits 402a,b may be used, without departing from the scope of the disclosure. Forinstance, in FIG. 4D, a single perforation or conduit 404 may be definedin and otherwise extended through the head 208 of the plunger 206. Asillustrated, the conduit 404 may be configured to receive the filamentwire 214 therein.

Those skilled in the art will readily recognize several other variationsthat the plunger 206 may assume while remaining within the scope of thepresent disclosure. The embodiments depicted in FIGS. 4A-4D are shownand described for illustrative purposes only and therefore should not beconsidered as limiting the disclosure to only those illustratedembodiments. Indeed, other configurations of the plunger 206, notnecessarily depicted or otherwise described herein, but nonethelessconfigured to generally interact with the filament wire 214 as discussedherein, are also contemplated as being within the scope of thedisclosure.

Therefore, the disclosed systems and methods are well adapted to attainthe ends and advantages mentioned as well as those that are inherenttherein. The particular embodiments disclosed above are illustrativeonly, as the teachings of the present disclosure may be modified andpracticed in different but equivalent manners apparent to those skilledin the art having the benefit of the teachings herein. Furthermore, nolimitations are intended to the details of construction or design hereinshown, other than as described in the claims below. It is thereforeevident that the particular illustrative embodiments disclosed above maybe altered, combined, or modified and all such variations are consideredwithin the scope and spirit of the present disclosure. The systems andmethods illustratively disclosed herein may suitably be practiced in theabsence of any element that is not specifically disclosed herein and/orany optional element disclosed herein. While compositions and methodsare described in terms of “comprising,” “containing,” or “including”various components or steps, the compositions and methods can also“consist essentially of” or “consist of” the various components andsteps. All numbers and ranges disclosed above may vary by some amount.Whenever a numerical range with a lower limit and an upper limit isdisclosed, any number and any included range falling within the range isspecifically disclosed. In particular, every range of values (of theform, “from about a to about b,” or, equivalently, “from approximately ato b,” or, equivalently, “from approximately a-b”) disclosed herein isto be understood to set forth every number and range encompassed withinthe broader range of values. Also, the terms in the claims have theirplain, ordinary meaning unless otherwise explicitly and clearly definedby the patentee. Moreover, the indefinite articles “a” or “an,” as usedin the claims, are defined herein to mean one or more than one of theelement that it introduces. If there is any conflict in the usages of aword or term in this specification and one or more patent or otherdocuments that may be incorporated herein by reference, the definitionsthat are consistent with this specification should be adopted.

The invention claimed is:
 1. A selective fire switch, comprising: aswitch housing; a plunger having a head and a body, the body extendinglongitudinally from the head and at least partially into an openingdefined in the switch housing; a first post and a second post arrangedon opposing sides of the switch housing; and a filament wire coupled toand extending between both the first and second posts across the switchhousing, the filament wire being in contact with the plunger and therebysecuring the plunger in a seated configuration within the switchhousing.
 2. The selective fire switch of claim 1, wherein the filamentwire extends from the first post to the second post and back to firstpost from the second post.
 3. The selective fire switch of claim 1,wherein the first and second posts support the filament wire across theswitch housing in a substantially tangential relationship with respectto the head of the plunger.
 4. The selective fire switch of claim 1,wherein at least one of the first and second posts define a lateralextension that extends a short distance over the switch housing.
 5. Theselective fire switch of claim 1, wherein the filament wire is coupledto one or both of the first and second posts by at least one ofsoldering, welding, brazing, or mechanical fasteners.
 6. The selectivefire switch of claim 1, wherein at least one of the first and secondposts is electrically conductive and configured to apply a voltageacross the filament wire.
 7. The selective fire switch of claim 1 or 6,wherein the filament wire is configured to fail upon being subjected tothe voltage, and wherein, when the filament wire fails, the plunger isable to move from the seated configuration to an extended configuration.8. The selective fire switch of claim 1, wherein the first postcomprises an input stanchion and an output stanchion, the input andoutput stanchions being electrically conductive and structurally offsetfrom each other on a first side of the switch housing.
 9. The selectivefire switch of claim 1 or 8, wherein the filament wire comprises a firstportion coupled to the input stanchion and extending to the second postarranged on a second side of the switch housing, and a second portionextending from the second post and coupled to the output stanchion. 10.The selective fire switch of claim 1, further comprising at least onegroove defined in the head of the plunger and being configured toreceive or engage the filament wire as it extends across the switchhousing.
 11. The selective fire switch of claim 1 or 10, wherein thefilament wire comprises a first portion and a second portion and the atleast one groove comprises a first groove and a second groove defined onopposing sides of the head, the first groove being configured to engagethe first portion and the second groove being configured to engage thesecond portion.
 12. The selective fire switch of claim 1 or 10, whereinthe at least one groove is centrally defined on the head and thefilament wire rests within the at least one groove.
 13. The selectivefire switch of claim 1 or 10, wherein the at least one groove comprisesone or more conduits defined through the head and configured to receivethe filament wire therethrough.
 14. A method of operating a selectivefire switch, comprising: securing a plunger in a seated configurationwithin a switch housing with a filament wire that engages the plunger,the filament wire being coupled to and extending between a first postand a second post arranged on opposing sides of the switch housing andextending across the switch housing; applying a voltage across thefilament wire; burning the filament wire with the voltage; and movingthe plunger from the seated configuration to an extended configurationwith respect to the switch housing.
 15. The method of claim 14, whereinthe plunger has a head and a body extending longitudinally from the headand at least partially into an opening defined in the switch housing,and wherein securing the plunger in the seated configuration furthercomprises supporting the filament wire with the first and second postsin a substantially tangential relationship with respect to the head. 16.The method of claim 14 or 15, wherein supporting the filament wire withthe first and second posts further comprises supporting the filamentwire with a lateral extension defined on at least one of the first andsecond posts, the lateral extension extending a short distance over theswitch housing.
 17. The method of claim 14 or 15, further comprisingengaging the filament wire in or on at least one groove defined in thehead of the plunger.
 18. The method of claim 14 or 15, wherein movingthe plunger from the seated configuration to the extended configurationfurther comprises: engaging the body of the plunger on a togglemechanism arranged within the switch housing, the toggle mechanism beingspring loaded; and moving the plunger into the extended configurationwith the toggle mechanism once the filament wire is burned.
 19. Themethod of claim 14, wherein applying the voltage across the filamentwire comprises: supplying a current to the first post, the first postbeing electrically conductive; and conducting the current from the firstpost to the filament wire.
 20. The method of claim 14, wherein the firstpost comprises an input stanchion and an output stanchion, the input andoutput stanchions being electrically conductive and structurally offsetfrom each other, and wherein apply the voltage across the filament wirecomprises: supplying a current to the input stanchion; conducting thecurrent from the input stanchion to a first portion of the filament wirewhich extends to the second post; and conducting the current to theoutput stanchion via a second portion of the filament wire that extendsfrom the second post.
 21. A selective fire switch, comprising: a switchhousing; a plunger extending at least partially into an opening definedin the switch housing; an input stanchion and an output stanchionarranged on a first side of the switch housing, the input and outputstanchions being electrically conductive and structurally offset fromeach other; a post arranged on a second side of the switch housingopposite the first side of the switch housing; and a filament wirehaving a first portion coupled to the input stanchion and extending tothe post across the switch housing, and a second portion extending fromthe post across the switch housing and to the output stanchion, thefilament wire being in contact with the plunger and thereby maintainingthe plunger in a seated configuration within the switch housing.
 22. Theselective fire switch of claim 21, wherein the filament wire issupported across the switch housing between the input and outputstanchions and the post in a substantially tangential relationship withrespect to the plunger.
 23. The selective fire switch of claim 21,wherein at least one of the input and output stanchions and the postdefines a lateral extension that extends a short distance over theswitch housing.
 24. The selective fire switch of claim 21, wherein thefilament wire is coupled to at least one of the input and outputstanchions and the post by at least one of soldering, welding, brazing,or mechanical fasteners.
 25. The selective fire switch of claim 21,wherein the input and output stanchions are electrically conductive andconfigured to route a voltage through the filament wire and around thepost.
 26. The selective fire switch of claim 21 or 25, wherein thefilament wire is configured to fail upon being subjected to the voltage,and wherein, when the filament wire fails, the plunger is able to movefrom the seated configuration to an extended configuration.
 27. Theselective fire switch of claim 21, wherein the plunger has a head and atleast one groove defined in the head, the at least one groove beingconfigured to receive or engage the filament wire as it extends acrossthe switch housing.
 28. The selective fire switch of claim 21 or 27,wherein the at least groove comprises a first groove and a second groovedefined on opposing sides of the head, the first groove being configuredto engage the first portion of the filament wire and the second groovebeing configured to engage the second portion of the filament wire. 29.The selective fire switch of claim 21 or 27, wherein the at least onegroove comprises first and second conduits defined through the head andconfigured to receive the first and second portions of the filamentwire, respectively, therethrough.